Methicillin-resistant Staphylococcus Aureus Strains Research Articles

Comparison of the effectiveness of ceftobiprole and vancomycin in a rabbit model of methicillin-resistant Staphylococcus aureus induced meningitis.

Nosocomial meningitis may occur after procedures affecting the central nervous system or following traumatic injury. The causative infectious organism is commonly Staphylococcus aureus, a gram-positive bacterium. The aim of the present study was to compare the effectiveness of two antibacterial agents, ceftobiprole and vancomycin in an animal model of methicillin-resistant Staphylococcus aureus (MRSA) meningitis. The strain of MRSA used was ATCC 43300. The animals were divided into three groups and infected intracisternally with MRSA. Controls received no antibiotherapy while the ceftobiprole group received 25 mg/kg and the vancomycin group received 20 mg/kg intravenously. Blood and cerebrospinal fluid (CSF) samples were collected at three time points. All animals were euthanased at 73 hours after start of treatment. There was a significant difference (p<0.05) between both treatment groups and the control animals at 24 hours (drug trough) and 73 hours (one hour after third dose) after start of treatment in terms of CSF bacterial levels. At 73 hours there was a significant difference in survival between the control group and the two treatment groups but no difference between the treated animal survival rates. In conclusion, intravenous treatment with ceftobiprole and vancomycin appears to be equally effective in a rabbit model of MRSA meningitis.

Discovery of N,N'-diarylurea molecules with activity against multidrug-resistant Staphylococcus aureus.

The emergence and global spread of methicillin-resistant Staphylococcus aureus (MRSA) pose a serious threat to public health, underscoring the urgent need for novel antibacterial interventions. Here, we screened 18 newly synthesized N,N'-diarylurea derivatives to identify compounds with activity against MRSA. Our investigations led to the discovery of a small molecule, SCB-24, which exhibited promising antimicrobial activity against MRSA USA300. Notably, SCB-24 demonstrated high activity even in the presence of 10% fetal bovine serum and showed excellent selectivity for bacterial over mammalian cells. SCB-24 also showed potent activity against various MRSA strains, including those resistant to second- and third-line antibiotics. Importantly, the efficacy of SCB-24 was inferior to that of vancomycin in MRSA-infected Galleria mellonella larvae. Overall, our findings suggest that SCB-24 has great potential as a new therapeutic for multidrug-resistant S. aureus infections.

Accessory Gene Regulator (agr) group polymorphisms in methicillin-resistant Staphylococcus aureus and its association with biofilm formation.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main causes of community- and hospital-acquired infections. The expression of virulence genes in S. aureus is arranged by regulators like the accessory gene regulator (agr). The present study aims to estimate phenotypic characteristics of S. aureus and investigate the occurrence of agr genes with their correlation to biofilm formation. In this study, 34 MRSA strains out of 100 S. aureus isolates were recovered in a variety of clinical samples. Phenotypic characterization and ability of biofilm formation were assessed. About 8(24%) of isolates were biofilm producers. The percentages of biofilm production among isolates were 3(37.5%), 2(25%), 3(37.5%) as strong, moderate, and weak, respectively. Furthermore, the resistance rates for all antibiotics were higher in biofilm producers and 76% of the isolates were staphyloxanthin producers, around 82% of the strains showed resistance to H2O2. Hemolytic activity was detected in 74% of the total isolates. The activity of the protease enzyme was 68%. The lipase enzyme was active in 79% of the tested S. aureus isolates. The majority of isolates were established to be agrI 84%, followed by agrII 53%, agrIII 32%, and 30% of the isolates have agr IV. Our study indicated that the majority of MRSA isolates were non-biofilm producers and the agr I is the most dominant type. Thus, agr I is not correlated with biofilm production.

[Investigation of the Antibacterial Synergistic Activity of Fosfomycin-Teicoplanin Combination in Methicillin-Resistant Staphylococcus aureus Strains Isolated from Various Clinical Sample].

The aim of this study was to investigate the detection of teicoplanin and fosfomycin antibiotic susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) strains by different methods and to evaluate the antibacterial synergistic effect of teicoplanin-fosfomycin combination by using checkerboard assay and time kill curve assay. Forty-five MRSA strains isolated from clinical samples in routine medical microbiology laboratory of Göztepe Prof. Dr. Süleyman Yalçın City Hospital were included in the study. In the first stage of the combination study, minimum inhibitory concentrations (MIC) were investigated by broth microdilution for teicoplanin and by both broth microdilution and agar dilution methods for fosfomycin. The combination of teicoplanin and fosfomycin was tested by the checkerboard method in 45 MRSA strains and combination effect was determined according to fractional inhibitory concentration index (ΣFIC) calculation. The synergistic effect and bactericidal activity of antibiotic combination were studied against a randomly selected strain from the strains used in the study by using time-kill method for 24 hours. As a result of teicoplanin and fosfomycin antibiotic susceptibility studies, all isolates were found to be susceptible to both antibiotics according to the susceptibility breakpoints determined by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). A synergistic effect was found in 22 (49%), additive effect in 22 (49%) and indifferent effect in one (2%) of the 45 strains studied with the checkerboard method. The mean ΣFIC of 45 isolates was found to be 0.5. In the combination study of the antibiotics of the isolate that was studied with time-kill method, synergism was detected for 1/8 MIC concentrations at 12th hour and 24th hour and synergism at 1/4 MIC concentration at sixth hour, 12th hour and 24th hour. In the combination study of 1/4 MIC concentrations of antibiotics, bactericidal effect was detected at sixth hour and this effect was observed to disappear at 12th and 24th hours. High rate of synergistic antibacterial effect of teicoplanin-fosfomycin combination on MRSA isolates was demonstrated as a result of in vitro tests. Such studies conducted on antibiotic-resistant bacterial infections will provide clinicians different treatment options and will contribute to increasing survival. As a result of this study, provided that it is supported by future clinical studies, it can be stated that the teicoplanin-fosfomycin combination may be an effective treatment option in community and hospital-acquired infections caused by MRSA.

Effects of sub-inhibitory concentrations of nafcillin, vancomycin, ciprofloxacin, and rifampin on biofilm formation of clinical methicillin-resistant Staphylococcus aureus.

Bacteria can be exposed to sub-MICs of antibiotics at the beginning and end of a dosing regimen, between doses, or during low-dose therapies. Growing evidence suggests that sub-MICs of antimicrobials can stimulate MRSA biofilm formation and alter the composition of the biofilm matrix. Pevious studies have found that sub-MICs of oxacillin, methicillin, and amoxicillin promote biofilm formation in some community-acquired MRSA (CA-MRSA). We evaluated biofilm induction by sub-MICs of four different classes of antibiotics in 44 CA-MRSA and 63 healthcare-associated MRSA (HA-MRSA) strains. Our study indicated that sub-MICs of nafcillin, vancomycin, ciprofloxacin, and rifampin frequently promote biofilm induction in clinical MRSA isolates. Strong biofilm induction in sub-MICs of nafcillin, ciprofloxacin, and rifampin was more frequent in HA-MRSA than in CA-MRSA. Antibiotic-induced biofilm formation depends on the antibiotic class, MRSA strain, and antibiotic resistance. Our results emphasize the importance of maintaining effective bactericidal concentrations of antibiotics to treat biofilm-related infections.

Triterpenoid saponin from Panax ginseng increases the sensitivity of methicillin-resistant Staphylococcus aureus to β-lactam and aminoglycoside antibiotics.

The triterpenoid saponins, ginsenosides, are the major bioactive compound of red ginseng and can exert various physiological activities. In the present study, we examined whether red ginseng extract (RGE) exerts antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). RGE had no bactericidal activity, at least in the range of dissolvable concentration. However, RGE reduced 0.03-0.25-fold the minimum inhibitory concentration (MIC) values of β-lactam antibiotics (oxacillin, ampicillin, carbenicillin, and cefazolin) and aminoglycoside antibiotics (kanamycin and gentamicin) against the two laboratory strains of MRSA. Moreover, the fractional inhibitory concentration index indicated the synergistic activity of RGE with each of the antibiotics. RGE also increased the kanamycin sensitivity of 15 MRSA strains isolated from human volunteers and increased the ampicillin sensitivity of five MRSA strains isolated from dairy cows diagnosed with bovine mastitis. In contrast, RGE did not alter the MIC values of fosfomycin, tetracycline, and erythromycin, suggesting that RGE acts selectively. In contrast, Triton X-100, which was reported to reduce the MIC value of β-lactam antibiotics to MRSA by increasing membrane permeability, reduced the MIC values of fosfomycin and tetracycline. These results indicate that RGE increases the bactericidal effect of antibiotics via a mechanism different from that used by Triton X-100. We found that ginsenoside Rg3 (Rg3), a component of RGE, was an essential compound that exhibits synergy activity with antibiotics. Furthermore, the non-natural compound K, which contains a common protopanaxadiol aglycon moiety with Rg3, also showed synergistic activity with antibiotics. Thus, Rg3 and compound K are potentially new antibiotic adjuvants against MRSA.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant organism that is prevalent worldwide. Therefore, the research and development of new agents against MRSA are required. We first found that ginsenoside Rg3 (Rg3) in red ginseng, made from the roots of Panax ginseng C. A. Meyer, increased the sensitivity of β-lactam antibiotics and aminoglycoside antibiotics to MRSA. Furthermore, we identified that compound K, an unnatural ginsenoside analog, also increased the sensitivity of antibiotics to MRSA, similar to Rg3. By contrast, neither Rg3 nor compound K increased the sensitivity of fosfomycin, tetracycline, and erythromycin to MRSA, suggesting that these act selectively. In the present study, the natural compound Rg3 and its structural isomer, compound K, are potentially new antibiotic adjuvants against MRSA. Currently, multiple antibiotics are used to treat MRSA, but the use of these adjuvants is expected to enable the treatment of MRSA with a single antibiotic and low concentrations of antibiotics.

Antibiotic susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated at tertiary care hospital in Riyadh, Saudi Arabia.

Staphylococcus aureus is an important human pathogen that has a major impact on public health. The objective of the present work was to determine the prevalence and the pattern of antibiotic susceptibility in S aureus (MRSA) isolates from the King Khalid University Hospital (KKUH) in Riyadh, Saudi Arabia. The isolates were collected from different body sites of infection and the antibiotic susceptibility was confirmed on the Vitek 2 system. A total of 371 MRSA isolates from clinical samples were received over a 12-month period from January 2021 to December 2021. The results showed that infection was predominant among males (55.8%) and most of the isolates occurred in the older age groups, with a mean age of 43.7 years and an age span from <1 to 89 years old. The majority (34.5%) recovered from wound infection followed by (14.6%) from blood. We have observed peaks of MRSA infections during the autumn, especially in September and November. All MRSA isolates were resistant to Amoxicillin + clavulanic acid, Ampicillin, Imipenem, Oxacillin, Cloxacillin, and Penicillin while all isolates were sensitive to Daptomycin and Nitrofurantoin. Furthermore, Vancomycin was resistant in (0.3%) of MRSA isolates, and (2.9%) was resistant to Linezolid. The current study concluded that MRSA strains had developed resistance toward 24 tested antibiotics, including the previous effective drugs vancomycin and linezolid. Therefore, there is an urgent need for continuous review of infection control practices to prevent any further spread of resistant strains.

Distinguishing methicillin-resistant Staphylococcus aureus from methicillin-sensitive strains by combining Fe3O4 magnetic nanoparticle-based affinity mass spectrometry with a machine learning strategy

Pathogenic bacteria, including drug-resistant variants such as methicillin-resistant Staphylococcus aureus (MRSA), can cause severe infections in the human body. Early detection of MRSA is essential for clinical diagnosis and proper treatment, considering the distinct therapeutic strategies for methicillin-sensitive S. aureus (MSSA) and MRSA infections. However, the similarities between MRSA and MSSA properties present a challenge in promptly and accurately distinguishing between them. This work introduces an approach to differentiate MRSA from MSSA utilizing matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) in conjunction with a neural network-based classification model. Four distinct strains of S. aureus were utilized, comprising three MSSA strains and one MRSA strain. The classification accuracy of our model ranges from ~ 92 to ~ 97% for each strain. We used deep SHapley Additive exPlanations to reveal the unique feature peaks for each bacterial strain. Furthermore, Fe3O4 MNPs were used as affinity probes for sample enrichment to eliminate the overnight culture and reduce the time in sample preparation. The limit of detection of the MNP-based affinity approach toward S. aureus combined with our machine learning strategy was as low as ~ 8 × 103 CFU mL−1. The feasibility of using the current approach for the identification of S. aureus in juice samples was also demonstrated.Graphical

Fabrication and antimicrobial properties of novel meropenem-honey encapsulated chitosan nanoparticles against multiresistant and biofilm-forming Staphylococcus aureus as a new antimicrobial agent.

Honey exhibits a broad spectrum of antibacterial activity against Gram-positive and Gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) ones. Chitosan (Cs) is a mucoadhesive polymer that also has antibacterial properties. Special attention has been paid to the design of polymeric nanoparticles (NPs) as new nano drug delivery systems to overcome bacterial resistance and its problems. The aim of the present study is to synthesize Cs-meropenem NPs with/without honey as an antibiofilm and antibacterial agent to inhibit Staphylococcus aureus. This study synthesized meropenem and honey-loaded Cs nanogels and subsequently characterized them by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), and DLS-zeta potential. Using the broth microdilution and crystal violet assays, the antibacterial and antibiofilm activity of meropenem and honey-loaded Cs nanogel, free meropenem, free honey, and free Cs NPs were investigated in vitro against MRSA strains. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) was also used to test the cytotoxicity of several Cs-NPs compound against the HEK-293 regular cell line. The average size of meropenem and honey-Cs-NPs was reported to be 119.885nm, and encapsulation efficiency was 88.33 ± 0.97 with stability up to 60 days at 4°C. The NPs showed enhanced antibiofilm efficacy against S. aureus at sub-minimum inhibitory concentrations. Additionally, the cytotoxicity of meropenem and honey-encapsulated Cs against the HEK-293 normal cell line was insignificant. Our findings suggested that meropenem and honey-Cs-NPs might be potential antibacterial and antibiofilm materials.

Molecular and epidemiological characterization of Staphylococcus aureus causing bovine mastitis in China

BackgroundStaphylococcus aureus is one of the most prevalent pathogens in bovine mastitis, which leads to substantial financial losses for the dairy industry. ResultsIn this study, S. aureus (n = 72) was isolated from 18 dairy farms in 15 provinces across China in 2021. The identification of these isolates at the species level was achieved by employing 16S rRNA sequencing. An isothermal amplification method for auxiliary detection of S. aureus was established, which can be employed not only for laboratory detection but also for point-of-care testing (POCT). Molecular characteristics of S. aureus mastitis in Chinese dairy cows were determined through MLST and spa typing. Finally, methicillin-resistant Staphylococcus aureus (MRSA) and MRSA resistance genes were detected using MIC and PCR amplification techniques. 72 isolates were identified as 12 sequence types (STs) and 7 clonal complexes (CC). ST1/CC1 was the dominant prevalent accounting for 33.3 % of the total, and exhibiting a wide distribution range. In terms of spa types, t114 was the dominant type, accounting for 31.9 % of the total, followed by t529 as the second major type. Four S. aureus strains were classified as MRSA according to their levels of oxacillin resistance (MIC ≥4 μg/mL). Among these four MRSA strains, one of them was found to be mecA positive. However, the presence of drug-resistance genes mecA and mecC was not detected in the remaining three MRSA strains, indicating the possible existence of new resistance genes. ConclusionsOur study investigated the prevalence of S. aureus mastitis in dairy cows in China, while also examined the molecular characteristics and MRSA strains. This information will help with the clinical monitoring, prevention, and control of S. aureus mastitis in dairy cattle.

A natural inhibitor of diapophytoene desaturase attenuates methicillin-resistant Staphylococcus aureus (MRSA) pathogenicity and overcomes drug-resistance.

At present, the inhibition of staphyloxanthin biosynthesis has emerged as a prominent strategy in combating methicillin-resistant Staphylococcus aureus (MRSA) infection. Nonetheless, there remains a limited understanding regarding the bio-structural characteristics of staphyloxanthin biosynthetic enzymes, as well as the molecular mechanisms underlying the interaction between inhibitors and proteins. Furthermore, the functional scope of these inhibitors is relatively narrow. In this study, we address these limitations by harnessing the power of deep learning techniques to construct the 3D structure of diapophytoene desaturase (CrtN). We perform efficient virtual screening and unveil alnustone as a potent inhibitor of CrtN. Further investigations employing molecular modelling, site-directed mutagenesis and biolayer interferometry (BLI) confirmed that alnustone binds to the catalytic active site of CrtN. Transcriptomic analysis reveals that alnustone significantly down-regulates genes associated with staphyloxanthin, histidine and peptidoglycan biosynthesis. Under the effects of alnustone, MRSA strains exhibit enhanced sensitivity to various antibiotics and the host immune system, accompanied by increased cell membrane permeability. In a mouse model of systemic MRSA infection, the combination of alnustone and antibiotics exhibited a significant therapeutic effect, leading to reduced bacterial colony counts and attenuated pathological damage. Alnustone, as a natural inhibitor targeting CrtN, exhibits outstanding antibacterial properties that are single-targeted yet multifunctional. This finding provides a novel strategy and theoretical basis for the development of drugs targeting staphyloxanthin producing bacteria.

Emerging threats of high biofilm formation and antibiotic resistance in clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates from Pakistan

ObjectivesThis multicenter study, conducted from a One Health perspective, aimed to comprehensively examine the prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) infections and their biofilm-forming capabilities in Pakistan. Phylogenetic analysis of the study isolates was also performed. MethodsA total of 150 MRSA isolates were screened from various clinical samples using Cefoxitin antibiotic discs. Genotypic confirmation was conducted through mecA, S. aureus-specific nuc, and 16S rRNA genes. Biofilm formation was assessed using Congo red agar (CRA) and slime layer quantification methods. The intercellular adhesion (ica) operon genes, specifically icaA and icaD, were detected. Phylogenetic analysis utilized the 16S rRNA sequences. Statistical associations between various parameters were determined using chi-square analysis. ResultsThe presence of the mecA gene was observed in 131 out of 150 isolates (87.3%). CRA identified 28% and 40% of isolates as strong and moderate biofilm producers, respectively, while 9.3% were classified as non-biofilm producers. The slime layer assay exhibited higher sensitivity, classifying only 4.7% of isolates as non-biofilm producers. Biofilm-forming genes icaA and icaD were detected in 85.3% and 86.7% of the isolates, respectively. Antibiotic resistance was more prevalent among biofilm-forming isolates, particularly against ciprofloxacin, levofloxacin, erythromycin, trimethoprim-sulfamethoxazole, and fosfomycin. Ceftaroline demonstrated efficacy irrespective of biofilm-forming abilities. Conversely, non-biofilm producers exhibited complete susceptibility to clarithromycin and tigecycline. ConclusionsClinical MRSA strains exhibit a substantial potential for biofilm formation, contributing to a resistant phenotype. Routine antibiotic testing in clinical settings that overlook the biofilm aspect may lead to the failure of empiric antibiotic therapy.

Genomic characterization and outbreak investigations of methicillin-resistant Staphylococcus aureus in a county-level hospital in China.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen contributing to healthcare-associated infections, which can result in multiple sites infections. The epidemiological characteristics of MRSA exhibit variability among distinct regions and healthcare facilities. The aim of this study was to investigate the molecular epidemiology and nosocomial outbreak characteristics of MRSA in a county-level hospital in China. A total of 130 non-repetitive MRSA strains were collected from December 2020 to November 2021. Whole-genome sequencing (WGS) was performed to identify antimicrobial resistance and virulence factors. Phylogenetic analysis was conducted to ascertain genetic diversity and phylogenetic relationships. Independent transmission scenarios were determined by the phylogeny derived from single nucleotide polymorphisms (SNPs) within the core genome. All the MRSA isolates were collected from the intensive care unit (30.00%, 39/130), the department of otorhinolaryngology (10.00%, 13/130) and the department of burn unit (9.23%, 12/130). The clinical samples mainly included phlegm (53.85%, 70/130), purulent fluid (24.62%, 32/130), and secretions (8.46%, 11/130). The resistance rates to erythromycin, clindamycin and ciprofloxacin were 75.38, 40.00, and 39.23%, respectively. All the isolates belonged to 11 clonal complexes (CCs), with the major prevalent types were CC5, CC59, and CC398, accounting for 30.00% (39/130), 29.23% (38/130), and 16.92% (22/130), respectively. Twenty sequence types (STs) were identified, and ST59 (25.38%, 33/130) was the dominant lineage, followed by ST5 (23.84%, 31/130) and ST398 (16.92%, 22/130). Three different SCCmec types were investigated, most of isolates were type IV (33.85%, 44/130), followed by type II (27.69%, 36/130) and type III (0.77%, 1/130). The common clonal structures included CC5-ST5-t2460-SCCmec IIa, CC59-ST59-t437-SCCmec IV and CC398-ST398-t034-SCCmec (-), with rates of 16.92% (22/130), 14.62% (19/130), and 13.84% (18/130), respectively. Only 12 panton-valentine leucocidin (PVL) positive strains were identified. Two independent clonal outbreaks were detected, one consisting of 22 PVL-negative strains belongs to CC5-ST5-t2460-SCCmec IIa and the other consisting of 8 PVL-negative strains belongs to CC5-ST5-t311-SCCmec IIa. Overall, our study indicated that the CC5 lineage emerged as the predominant epidemic clone of MRSA, responsible for nosocomial outbreaks and transmission within a county-level hospital in China, highlighting the necessity to strengthen infection control measures for MRSA in such healthcare facilities.

Bioisosteric replacement strategy leads to novel DNA gyrase B inhibitors with improved potencies and properties

The identification of novel 4-hydroxy-2-quinolone-3-carboxamide antibacterials with improved properties is of great value for the control of antibiotic resistance. In this study, a series of N-heteroaryl-substituted 4-hydroxy-2-quinolone-3-carboxamides were developed using the bioisosteric replacement strategy. As a result of our research, we discovered the two most potent GyrB inhibitors (WBX7 and WBX18), with IC50 values of 0.816 µM and 0.137 µM, respectively. Additional antibacterial activity screening indicated that WBX18 possesses the best antibacterial activity against MRSA, VISA, and VRE strains, with MIC values rangingbetween0.5and 2 µg/mL, which was 2 to over 32 times more potent than that of vancomycin. In vitro safety and metabolic stability, as well as in vivo pharmacokinetics assessments revealed that WBX18 is non-toxic to HUVEC and HepG2, metabolically stable in plasma and liver microsomes (mouse), and displays favorable in vivo pharmacokinetic properties. Finally, docking studies combined with molecular dynamic simulation showed that WBX18 could stably fit in the active site cavity of GyrB.

Rabbit meat as a potential source of multidrug-resistant and enterotoxigenic

Staphylococcus aureus in rabbit meat is a consequence of insufficient hygienic handling and improper processing posing a major health hazard. This study was conducted to assess rabbit meat as a potential source of Staphylococcus species, particularly Staphylococcus aureus (S. aureus). Furthermore, the identified S. aureus isolates were tested for the detection of the mecA virulence gene of methicillin-resistant Staphylococcus aureus (MRSA) and enterotoxin encoding genes (Sea, Seb, Sec, and Sed). A total of 80 samples of different rabbit meat cuts represented by shoulder, ribs, loin, and thigh (20 of each) were collected from various markets of different sanitation levels. The results obtained revealed that the mean counts of Staphylococcus species were 7.40×105 , 7.58×105 , 7.60×105 and 8.29×105 CFU/g in the examined shoulder, ribs, loin and thigh samples, respectively. Out of 17 identified S. aureus isolates, 5 (29.4%) strains were characterized by the presence of the mecA gene. A large proportion of the isolates obtained were resistant to at least three antibiotics. Enterotoxins were evaluated by ELISA. The results showed that three strains isolated from shoulder produced Sea, Seb, and Sec enterotoxins, the strains isolated from ribs failed to produce enterotoxins, while two strains isolated from loin and thigh produced Sea enterotoxin. The presence of S. aureus, especially MRSA strains, in the examined rabbit meat indicates the necessity of enforced application of strict hygienic measurements.

On-site detection of methicillin-resistant Staphylococcus aureus (MRSA) utilizing G-quadruplex based isothermal exponential amplification reaction (GQ-EXPAR)

Methicillin-resistant Staphylococcus aureus (MRSA) has a high incidence in infectious hospitals and communities, highlighting the need for early on-site detection due to its resistance to methicillin antibiotics. The present study introduces a highly sensitive detection system for mecA, a crucial methicillin marker, utilizing an RCA-based isothermal exponential amplification reaction. The G-quadruplex-based isothermal exponential amplification reaction (GQ-EXPAR) method designs probes to establish G-quadruplex secondary structures incorporating thioflavin T for fluorescence. The system, unlike conventional genetic detection methods, works with portable isothermal PCR devices (Isoquark), facilitating on-site detection. A detection limit of 0.1 fmol was demonstrated using synthetic DNA, and effective detection was proven using thermal lysis. The study also validated the detection of targets swabbed from surfaces within bacterial 3D nanostructures using the GQ-EXPAR method. After applying complementary sequences to the padlock probe for the target, the GQ-EXPAR method can be used on various targets. The developed method could facilitate rapid and accurate diagnostics within MRSA strains.

Comparison of broth microdilution and E-test for susceptibility of MRSA to vancomycin

Introduction: Healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) developed soon after the introduction of methicillin. These bacteria have shown resistance to multiple drugs and therefore vancomycin became the antibiotic of choice for treatment of MRSA infections. Vancomycin is a bactericidal antibiotic that acts by inhibiting bacterial cell wall synthesis. This study aimed to compare broth microdilution (BMD) and E-test in determining vancomycin minimum inhibitory concentration (MIC) against MRSA.Methods: A total of 30 clinical isolates of MRSA were acquired from Colombo South Teaching Hospital, Sri Lanka. These MRSA strains were identified by cefoxitin disk diffusion and the vancomycin MIC was determined through BMD and E-test. The Kruskal-Wallis test was applied to test if the samples originated from the same distribution with post hoc determination of the correlation between methods using the Mann-Whitney U test.Results: All 30 MRSA isolates were 100% vancomycin susceptible (≤2 μg/mL) irrespective of methodology, according to the Clinical and Laboratory Standards Institute (CLSI) established breakpoints. However, the E-test MIC values were 1 to 2 dilutions higher than those of BMD. A statistically significant difference between vancomycin MICs of BMD and E-test (p = &lt;0.00001) was calculated which indicated a difference in accuracy.Conclusion: Due to cost, convenience, and the ability to detect vancomycin intermediate Staphylococcus aureus (VISA), exploring the possibility of using E-test as an alternative to BMD is worthwhile.

Role of tcaA, a potential target as a ceftobiprole resistance breaker, in MRSA β-lactam resistance

ObjectivesUsing a random forest algorithm, we previously found that teicoplanin-associated gene A (tcaA) might play a role in resistance of methicillin-resistant Staphylococcus aureus (MRSA) to β-lactams, which we have investigated further here. MethodsRepresentative MRSA strains of prevalent clones were selected to identify the role of tcaA in the MRSA response to β-lactams. tcaA genes were deleted by homologous recombination in the selected MRSA strains, and antibiotic susceptibility tests were applied to evaluate the effect of tcaA on the minimum inhibitory concentrations (MICs) of glycopeptides and β-lactams. Scanning electron microscopy, RNA sequencing, and quantitative reverse transcription-polymerase chain reaction were performed to explore the mechanism of tcaA in MRSA resistance to β-lactams. ResultsThe MIC of penicillin plus clavulanate decreased from 3 mg/L to 0.064 mg/L and that of oxacillin decreased from 16 to 0.5 mg/L when tcaA was knocked out in the LAC strain. Compared with wild-type MRSA isolates, when tcaA was deleted, all selected strains were more susceptible to β-lactams. Susceptibility to ceftobiprole was restored in the ceftobiprole-resistant strain when tcaA was deleted. tcaA knockout caused “log-like” abnormal division of MRSA, and tcaA deficiency mediated low expression of mecA, ponA, and murA2. ConclusionsMachine learning is a reliable tool for identifying drug resistance-related genes. tcaA may be involved in S. aureus cell division and may affect mecA, ponA, and murA2 expression. Furthermore, tcaA is a potential resistance breaker target for β-lactams, including ceftobiprole, in MRSA.

Extracting and evaluating the antibacterial activity of carvacrol from Plectranthus Amboinicus essential oil against Staphylococcus aureus and MRSA

The essential oil of Plectranthus amboinicus was extracted through steam distillation. Carvacrol, the major constituent of the oil, was identified and found to make up 60.003% of the oil. Carvacrol was isolated using column chromatography with silica gel (200-430 mesh) and hexane: ethyl acetate (100:1) eluent solvent mixture, resulting in a high purity of 98.32%. Antimicrobial activity testing revealed that both Staphylococcus aureus and MRSA strains were sensitive to carvacrol and Plectranthus amboinicus essential oil (20 mg/mL). The antibacterial zone diameters were measured to be 20.20 ± 0.36 mm and 17.33 ± 0.32 mm for S. aureus, and 24.23 ± 0.47 mm and 21.53 ± 0.55 mm for MRSA, respectively. The minimum inhibitory concentration (MIC) of carvacrol against S. aureus and MRSA was determined to be 0.5 mg/mL. The minimum bactericidal concentration (MBC) against S. aureus was 1 mg/mL, while it was 0.5 mg/mL against MRSA.

ST8-t008-SCCmec IV methicillin-resistant Staphyloccoccus aureus (MRSA) in retail fresh cheese

This study reports the finding of 3 ST8-t008-SCCmec IVa (2B) MRSA strains in fresh cheese purchased within a single market in Costa Rica. In line with the finding of the resistance genes mecA, blaZ, mph(C), and msr(A) in their genomes, these bacteria showed phenotypic resistance to multiple β-lactams and erythromycin. Besides, they carry genes for acquired resistance to aminoglycosides (aph(3′)-III) and fosfomycin (fosD), mutations in genes associated with fluoroquinolone resistance (gyrA-85 and parC-80), and genes for a myriad of virulence factors, including adhesins, hemolysins, and exotoxins. Our strains share multiple genomic features with MRSA from the USA300 lineage, which is a widely distributed and highly virulent strain implicated in community infections. As a result, consuming these or similar products could lead to multidrug (MDR) infections in susceptible individuals. These results highlight safety deficiencies in cheese production practices and emphasize the risk of foodborne transmission of hard-to-treat ST8 MRSA strains.